The present invention relates to a float switch of an internal combustion engine such as an outboard motor or the like and, more particularly, to a control apparatus of an internal combustion engine in which absence of a function maintaining fluid of the internal combustion engine can be positively detected by use of a small-sized, lightweight and easily attachable float switch, thereby making it possible to prevent damage of the engine.
The invention also relates to an apparatus to prevent overheating of an outboard engine and, more particularly, to a warning apparatus for detecting an occurrence of a cause of an overheating of the outboard engine and generating a warning.
In internal combustion engines, a function maintaining fluid such as cooling water, lubricating oil or the like (hereinafter referred to as a fluid) is allowed to flow through each section in order to make each section function effectively and thereby make the most of the performance of the engine.
If this fluid is lacking or does not flow through the engine, the engine will be damaged due to overheating or the like. For example, in a water-cooled outboard engine, if the coolant is not supplied to the engine due to a failure of the coolant pump or a plugging of an inlet passage for the coolant, the engine will overheat and be damaged. Or, the engine can be similarly damaged due to the lack of lubricating oil, failure of the pump for the lubricating oil, or the like.
Therefore, hitherto, causes of the occurrence of engine damage have been detected by various types of sensors to prevent engine damage. For example, a temperature sensor is attached to the cylinder head or the like of the engine and, when the engine overheats and exceeds a preset temperature, this sensor generates a signal so that the warning apparatus or control apparatus for reducing the rotating speed of the engine is made operative.
However, in such a temperature detecting system, the temperature is detected while the engine is overheating, so that it is difficult to set the temperature, and the temperature of the detecting portion changes due to various factors of the engine. Consequently, there are drawbacks such that the set temperature has to be adjusted and checked depending on the specifications of the engine, and attention must be also paid to the attaching position and attaching method, and the like.
On the other hand, there is known another system equipped with what is called a float switch in which a float member is vertically movably inserted and attached into a pipe member which is vertically disposed, and in which a limit switch is attached at the position corresponding to the level of the height of fluid to be detected; and the limit switch in the pipe member is opened or closed by means of a magnetic material attached to this float, thereby detecting the presence or absence of the fluid.
In such a conventional float switch, however, the length of pipe member has to be changed in dependence upon the height of the fluid to be detected or upon the portion where the switch is attached. In addition, since the fluid surface is detected by way of the vertical movement of the float inserted movably into the pipe member, there are drawbacks such that a long pipe member is inevitably needed for allowing the contact to be opened or closed, and the mechanism becomes large. Further, if it is intended to miniaturize the detecting mechanism by making the pipe member short, the vertical movement range of the float is narrowed, so that the opening or closing of the contact becomes difficult, causing the operation of the limit switch to become uncertain.
Therefore, in such a conventional float switch, it is difficult to make the float switch small and of light weight and to set the attaching position, so that it is difficult to realize a control apparatus which can positively detect the absence of the fluid, such as the coolant or the like, so as to prevent damage of the engine.
On the other hand, generally in water-cooled outboard engines, the cooling water is pumped up by a water pump provided in the gear casing, and this water is circulated in the jacket of the cylinder and thereafter is drained to the outside. Therefore, in the case where the inlet for the cooling water is choked or the water pump fails to operate, the cooling water is not circulated and the engine overheats, so that the cylinder and piston are damaged.
In addition, in the case where a propeller having a pitch smaller than the set standard value is used or a load is light even when the standard propeller is used, the rotating speed of the engine increases more than the speed as needed, so that there is a drawback such that the service life of the engine is remarkably reduced.
Moreover, recently many outboard engines of the separation oil supply type have been used. However, in the case where the quantity of oil falls below a specified value, it is necessary to inform the operator as to the lack of oil.
The warning apparatus for an outboard engine is required because of the above-mentioned viewpoints.
As conventional warning apparatuses for an outboard engine, for example, there are known such apparatuses as disclosed in the Official Gazettes of Japanese Patent Application Laid-Open Nos. 146011/1981, 10772/1982 and 131820/1982. In these warning apparatuses, the temperature of the cylinder head portion of the engine is detected by a temperature sensor attached to the cylinder head of the engine. When the temperature exceeds a preset temperature, a buzzer or the like is made operative or the rotating speed of the engine is simultaneously controlled. In this way, the operator is warned as to the overheated state of the engine. Also, when the oil level is low, the buzzer or the like is likewise made operative, or the rotating speed of the engine is controlled.
In the foregoing conventional warning apparatuses, the set temperature of the temperature sensor attached to the cylinder head portion corresponds to a value while the temperature is increasing after the cooling water of the engine was extinguished. Thus, there is a problem such that it is difficult to select the value that is set. In other words, in dependence on the value of the set temperature, a situation such that a warning is generated in the normal operating state or the generation of the warning may occur too late. Further, means such as grease or the like is required for allowing the heat of the cylinder head to be sufficiently transferred to the temperature sensor, causing an inconvenience such that it is troublesome. In addition, it is necessary to change the set value of the temperature sensor for every engine, resulting in a drawback such that many kinds of temperature sensors having different set values are needed.